1. Field of the Invention
The present invention pertains to a camera module and, more particularly, to a camera module reduced in thickness and in weight by forming an image pickup element and a signal processing element so as to have a stack structure.
2. Description of the Related Art
In recent years, camera modules have been positively employed for cellular telephones, portable computers, etc. Therefore, camera modules are required to be reduced in size, in thickness, and in weight.
In the present invention, as an example, a description will be given referring to a camera module that uses a CCD as a semiconductor image pickup element. Semiconductor image pickup elements (a CMOS sensor, for example) other than the CCD can be used.
A description will be given of the structure of a conventional camera module with reference to FIG. 17. First, a CCD102 is mounted on a mounting board 101. A lens 105 used to converge light from the outside is fixed to a lens barrel 106 above the CCD102. The lens barrel 106 is held by a lens holder 107, and the lens holder 107 is mounted on the mounting board 101 by means of a lens-fastening screw 108 (see patent Publication 1 mentioned below, for example).
The CCD, which is an abbreviation for Charge Coupled Device, functions to output an electric charge proportional to the intensity of light converged by the lens 105. The lens barrel 106 has its side face like a screw (not shown), and functions to focus the lens 105 by being rotated.
A chip component 103 and a reverse-side chip component 104 are mounted on the obverse face and the reverse face, respectively, of the mounting board 101. DSPs, driver ICs, capacitors, resistors and diodes can be adapted as these chip components. The DSP, which is an abbreviation for Digital Signal Processor, functions to process digital signals sent from the CCD at high speed. The driver IC functions to pressurize a driving signal sent from the DSP and transfers an electric charge stored in the CCD, in order to drive the CCD.
A description will be given of a method for assembling this camera module with reference to FIG. 18. Referring first to FIG. 18(A), the mounting board 101 is prepared, and the reverse-side chip component 104 is mounted on the reverse face of the mounting board 101.
Referring next to FIG. 18(B), the CCD 102 and the chip component 103 are mounted on the obverse face of the mounting board 101.
Finally, referring to FIG. 18(C), the lens barrel 106 to which the lens 105 is fixed is fixed to the lens holder 107, and the lens holder 107 is fixed to the mounting board 101 by means of the lens-fastening screw 108. In order to fix the lens holder 107 by means of the lens-fastening screw 108, a through hole is formed in a corresponding part. A conventional camera module using the mounting board 101 is completed according to this method.
Patent Publication 1: Japanese Unexamined Patent Publication No. 2002-185827 (Page 4, FIG. 2)
However, the conventional camera module has had the following problems.
Since the elements, such as the DSP and the driver IC, that are used to process the signal of the CCD 102 and to drive it are flatly mounted on the mounting board 101, the mounting board 101 is required to have a large area, and this has hindered size reduction of the camera module.
Additionally, the mounting board 101 is inherently unnecessary. However, in terms of a manufacturing method, the mounting board 101 has been used to stick electrodes together and to fix the lens holder 107. Therefore, the mounting board 101 could not be eliminated.